A level shifter is an electrical component that converts digital signals from a low-side voltage domain to into a high-side voltage domain. The input signals are connected to a ground in the low-side domain, while the output signals are connected to a ground in the high-side domain. Both the low-side ground and high-side ground are separate and electrically isolated from each other.
One type of level shifter is an Ultra-high Voltage (UHV) level shifter. UHV level shifters operate to convert a control signal from a low-side control circuit into a driver signal for a high-side gate driver of a half bridge circuit. A low-side control circuit generates the control signal and further drives a low-side switch of the half-bridge circuit. Therefore, the negative supply of the low-side domain is connected to the negative supply of the half-bridge. UHV level shifters typically are used in LLC converters or motor drives and have a half bridge supply voltage of approximately 400 V. In other words, the voltage difference between the high-side domain and low-side domain oscillates from 0 V to 400 V and back.